This invention relates generally to so-called "outboard motors" or units each comprising an engine, a propeller, a mechanism for transmitting the engine power to the propeller, auxiliary devices, and a frame for supporting and holding together these parts as a unit. This unit, which will hereinafter be referred to as an outboard engine, is mountable in a freely dismountable manner on a stern part of a boat or like marine surface vessel. More particularly, the invention relates to a system for controlling the engine of an outboard engine.
In general, reduction of the size and weight of an outboard engine is sought by using a simple internal-combustion engine such as, for example, a two-stroke-cycle engine having a separate lubrication system and means for introducing cooling water from the outside. Such an engine, however, is accompanied by risks such as deficiency of lubricating oil due to carelessness on the part of the operator or clogging of the cooling water inlet by foreign matter. Accordingly, it has heretofore been a practice to provide a warning lamp or a buzzer to warn the operator when the quantity of the lubricating oil falls below a minimum level or when the engine overheats thereby to prevent oil shortage or overheating. These measures, however, have not been fully effective in cases such as that wherein the operator fails to notice the warning indication and thereby does not reduce the engine speed.
Accordingly, in a known engine for marine use, means are provided to compulsorily reduce the engine speed prior to the occurrence of the above described abnormalities during navigation over water (as disclosed in, for example, Japanese patent application Laid-Open (Kokai) No. 85210/1985). In this technique, however, the engine speed is reduced by causing the ignition system of the engine to undergo repeated alternations of ignition and non-ignition. As a consequence, each spark plug is wetted by the liquid fuel at each instance of non-ignition, similarly as in the case of flooding due to excessive operation of the starter mechanism without ignition, whereby there is the possibility of misfiring.